Things to consider before brake upgrade

One of the typical upgrades is to upgrade the brakes in order to shorten the braking distance, improve the pedal feel etc... Upgrade can be done in many ways, by changing the brake pads, rotors and ultimately by changing the calibers.

My setup is now totally different from stock, details are here: BemariM3Ex brake system.

Before you pay $2000 for your new Big brake system, you need to consider following things:

1. Do I need to change the master cylinders? Typically bigger brake calibers have more pistons and therefore require more fluid to be pushed to the calibers. Rule is: More fluid->Bigger master cylinder, more pressure->smaller master cylinder. Also a bigger reservoir might be needed.

2. Brake balance, will I have too much front brake after the upgrade? Brake balance is affected if really aggressive calibers and pads are installed to front and rear brakes are not braking at all. In a modern car, this might not be an issue since almost all modern ABS systems are equipped with a system called EBD, Electronic Brake Distribution and it will take care of the brake balance. If not, a brake proportioning device might be required. Remember that in full rear position, brake balance needs to be at the front wheels, otherwise the car will spin.

3. Do I need bigger wheels? This is quite obvious, make sure calibers work with the wheels since bigger calibers typically require bigger wheels.

3. Are my tires good enough? Biggest single contributor is actually the tire itself. If the tire locks at 0.9g, it will still lock at 0.9g with the bigger brakes...

4. Should I keep my ABS? ABS is one of the limiting factors. Below is one log from my car and shows how ABS will limit the braking performance.

Graph shows speeds from the ABS sensors and long acceleration.

Brakes are applied at 870.57sec. At 870.90, front right wheel locks, pressure is reduced and wheel starts turning again. Long acceleration is about 1g. At 871 sec, front left wheel locks and pressure is reduced. At 871.5, rear right wheel starts to lock and pressure to both rear wheels is reduced since M3 is equipped with 3-channel ABS where both rear wheels are controlled by the same channel.

So, in my case, tires and ABS are the limiting factor and the best deceleration I can achieve is about 1g. I'm still learning how to brake without ABS, more to come on this topic so stay tuned...